Ground-based photometric measurements

Resolution in space, time, magnetic field strength, intensity variance, and wavelength all are used to isolate the signals from sunspots, plage, network, and nonmagnetic areas. Ground data has demonstrated the dominance of sunspots in causing irradiance variance on time scales of hours to months, the near balance of spot deficit and facular excess emission, and the low level of irradiance variation caused by nonmagnetic regions. Present techniques limit the accuracy of comparison with direct irradiance measures, and improvements should be made. Goals for ground-based photometry for the next cycle are suggested. 59 references